1. Field of the Invention
The present invention generally relates to magnetic disks and magnetic disk recorders using the same and, more particularly, is directed to a magnetic disk and a magnetic disk recorder using the same to which the sampled servo tracking method, for example, can be applied.
2. Description of the Related Art
In the magnetic recording techniques, a so-called sampled servo tracking method has been known as one of the tracking servo methods. In a disk to which the sampled servo tracking method is applied, a servo zone and a data zone are alternately and repeatedly provided on each of plurality of annular tracks on the disk. Signals for control are reproduced from the servo zone, and a data signal is recorded on and reproduced from the data zone in accordance with a clock signal or the like reproduced from the servo zone. Thus, in the thus arranged sampled servo tracking method, a space or distance along a track between the adjacent servo and data zones is required to be very small.
Further, according to the sampled servo tracking method, since the signals recorded in the servo zone must not be erased at all, the sampled servo tracking method has been employed to magneto-optical disks. This is because, in the magneto-optical disk, the signals in the servo zone can be recorded by pregrooves so as not to be erased.
However, when the sampled servo tracking method is employed in a magnetic disk recorder, the following problem arises. For example, when an operation is changed to the reproduction of the servo zone from the recording of the data zone, a recording output current of a recording amplifier does not drop to zero immediately but gradually decreases to zero due to a transient residual output current of the amplifier. Thus, data at a header portion of the servo zone following a just recorded data zone is overwritten and may be erased by the transient residual output current from the recording amplifier.
In order to eliminate this problem in the magnetic disk recorder, a space, corresponding to a period between a timing of the change from the recording of the data zone to the reproduction of the servo zone and a timing when the recording output current of the recording amplifier drops to zero, must be provided between the last portion of the data zone and the header portion of the servo zone. Thus, it becomes difficult to correctly maintain the relation between the data zone and the servo zone owing to the space. Accordingly, it has been impossible to employ the sampled servo tracking method in the magnetic disk recorder.